NATE Gas Heating Practice Exam

What is a common consequence of improper venting in a furnace?

1. Increased flue gas temperature

2. Decreased heat transfer efficiency

3. Backdrafting of combustion gases

4. Enhanced air filtration

The correct answer is: Backdrafting of combustion gases

Improper venting in a furnace can lead to backdrafting of combustion gases, which occurs when the exhaust gases flow back into the living space instead of being expelled outside. This reversal of airflow can happen due to issues such as blockages in the venting system, negative pressure in the home, or other malfunctions. Backdrafting is particularly dangerous as it can bring toxic gases, like carbon monoxide, into the occupied areas of a building, posing a serious health risk to inhabitants. Adequate venting is crucial for ensuring that combustion byproducts are safely removed from the furnace and do not enter the home. While other options may relate to furnace performance, they do not directly address the immediate and critical consequence of improper venting, which is the risk of backdrafting harmful gases.